The present invention relates to a magnetic head slider and a magnetic disk drive. In particular, the present invention is concerned with a magnetic head slider of a low flying type for attaining high reliability and high density recording, as well as a magnetic disk drive with the magnetic head slider mounted thereon.
The magnetic disk drive has recently been becoming increasingly smaller in size and larger in capacity and data recorded on a recording medium (a magnetic disk) have been becoming increasingly higher in recording density. With this trend, it is necessary to diminish the space between a magnetic head slider and a magnetic disk, i.e., the flying height of the magnetic head slider. A magnetic head slider able to fly stably at a low flying height has been proposed. For example, Patent Literature 1 (Japanese Patent Laid-Open No. 6-325530) discloses such a magnetic head slider that a surface (stepped surface) depressed from a plane portion of a flying rail (an air bearing rail) of a slider is formed on a leading side of the flying rail and the depth (height of the stepped portion) of the stepped surface is set at an extremely small value (700 nm or less) to attain a constant flying height that does not depend on the peripheral velocity of the magnetic disk. The slider having a stepped portion of such an extremely small depth is designated a microstep slider.
Patent Literature 2 (Japanese Patent Laid-Open No. 2000-21109) discloses another magnetic head slider of a low flying type. In this slider, a very small lug having a height equal to or larger than a step depth (height) is formed on a stepped surface provided on a leading side of a flying rail of a slider, whereby the slider is difficult to rotate while falling forward and a front edge of the stepped surface is prevented from contacting the disk surface.
If the flying height of a magnetic head slider varies and the magnetic head slider comes into contact with the surface of a magnetic disk while flying over the magnetic disk, an air bearing surface (the surface opposed to the disk) of the magnetic head slider is pulled with a frictional force and the magnetic head slider rotates about a pivot (a load acting point) of a suspension and assumes a forwardly falling attitude. As a result, a front edge portion on a leading end side of the magnetic head slider comes into contact with the disk surface, whereupon an air inlet port is blocked and there no longer is an air flow on the air bearing surface side of the magnetic head slider. Consequently, a flying force is not created in the magnetic head slider and the magnetic head slider is put in continuous contact with the magnetic disk surface while retaining its forwardly falling attitude, thus giving rise to the problem that the magnetic disk is damaged.
In a magnetic disk drive using a smooth magnetic disk for attaining a low flying height of a magnetic head slider, a large frictional force poses a serious problem. With a large frictional force, the magnetic head slider assumes a forwardly falling attitude and, therefore, preventing contact of the front edge portion on the leading end side of the magnetic head slider with the magnetic disk surface is an important subject for preventing damage to the recording medium and for ensuring reliability. To solve this problem, a method involving chamfering (curving) the front edge portion on the leading end side to increase the area of contact and thereby decrease a contact stress (surface pressure) has been proposed. However, since chamfering is usually performed by machining of large variations, it greatly contributes to the generation of a change in flying height. Such a change in flying height causes malfunctions in data read and write. Thus, this method is not an effective approach for preventing damage of the magnetic disk caused by contact therewith of the front end portion on the leading end side.
As described in Patent Literature 2, if a very small lug is formed on the stepped surface provided on the leading side of the flying rail of the magnetic head slider so as to prevent contact of the front edge portion on the leading end side of the magnetic head slider with the disk surface, a certain height of the lug restricts reduction in flying height and as the case may be it is impossible to attain a low flying height.
Decreased atmospheric pressure causes excessive reduction in flying height of the magnetic head slider. More particularly, in case of using the magnetic disk drive at a high elevation, the flying height lowers due to reduction of the atmospheric pressure. When the flying height lowers excessively, the magnetic head slider assumes a forwardly falling attitude, thus giving rise to the problem that the front edge portion on the leading end side of the magnetic head slider comes into contact with the magnetic disk surface and the recording medium is damaged.